White blood cell (WBC) count, or the measure of white blood cells in the blood, is a reliable and widely used marker that reflects inflammation throughout the body, according to background information in the article. People who smoke or have acute or chronic infections generally have a higher WBC count. Previous studies have linked WBC count to other chronic conditions, including cardiovascular disease, hypertension and diabetes. Some evidence also suggests that inflammation is related to the development and progression of cancer, but few researchers have examined whether WBC count and other markers of inflammation can predict cancer, the authors write.
To assess this potential link, Anoop Shankar, M.D., Ph.D., National University of Singapore, and colleagues studied 3,189 Australians with an average age of 65.9 years who were part of the Blue Mountains Eye Study. All of the participants were born before Jan. 1, 1943, and were free of cancer when they were initially evaluated between 1992 and 1994. By the end of the study, on Dec. 31, 2001, 212 participants had died of cancer.
Even when controlling for other factors that might affect WBC count, including smoking, diabetes and aspirin use, individuals in the highest quartile of WBC count (the 25 percent of the study population with the highest WBC counts) had an increased risk of death from cancer, the authors report. The association appeared especially strong for participants who died of lung cancer. "In our study, WBC count was associated with cancer mortality, even after adjusting for smoking status," the authors write. "In subgroup analyses, the association was also present among those who never smoked, suggesting that the observed association between WBC count and cancer mortality is not fully explained by smoking."
The study also suggests that aspirin may have a greater protective effect against cancer for those with high WBC, as the risk of cancer death was higher among those with high WBC who did not take aspirin weekly than among those who did.
"These data provide important new epidemiological evidence of an essential link between inflammation and cancer mortality," the authors write. "Our findings suggest that local inflammatory processes that have long been known to be associated with tumor progression may be reflected in the systemic inflammatory marker of higher WBC count."
(Arch Intern Med. 2006; 166:188-194. Available pre-embargo to media at www.jamamedia.org.)
Editor's Note: This study was supported in part by project grants from the Australian National Health and Medical Research Council, Canberra.